1. Field of the Invention
The present invention relates to a part molding method for manufacture of a lens-fitted photo film unit. More particularly, the present invention relates to a part molding method for manufacture of a lens-fitted photo film unit, in which convenience in manufacturing plural types of lens-fitted photo film units is increased.
2. Description Related to the Prior Art
A lens-fitted photo film unit includes a photo film housing or body, which incorporates a simple exposure mechanism, is pre-loaded with unexposed photo film, and is covered inside a cardboard wrapper or packaging which has a printed pattern. There are two types of the lens-fitted photo film unit, including a flash built-in type and a flashless type.
In the flashless type, an exposure aperture is formed to define a range on a photo film to be exposed, and located between a photo film supply chamber and a cassette containing chamber. The photo film housing of the flashless type is constituted by an exposure unit or photo film containing unit, a front cover and the rear cover. The exposure unit includes the exposure aperture, the photo film supply chamber and the cassette containing chamber. The outer wall of the photo film supply chamber has a curve protruding toward the front in a partially cylindrical shape. The front and the rear of the exposure unit are covered by the front cover and the rear cover. Each of the parts is formed by injection molding.
In the flash built-in type, a printed circuit board including parts for the flash circuit is mounted on an outer wall of the photo film supply chamber in a position near to the exposure aperture. An interval between the exposure aperture and the photo film supply chamber is determined great in the exposure unit. The front cover and the rear cover have a relatively greater length than a length of those for the flashless type. The front cover further includes a flash emitter window and a warning message indicating electrical danger of the flash device.
To reduce the cost in manufacturing the lens-fitted photo film unit of the flash built-in type and the flashless type, there is a suggestion of using the exposure unit or the rear cover for the flash built-in type also for the flashless type. Two types of the front cover should be produced, including a type having the flash emitter window and the warning message and another lacking them. For this purpose, two kinds of mold sets should be used, including one kind having subsidiary core/cavity combinations for molding the flash emitter window and the warning message, and another lacking such subsidiary core/cavity combinations.
To mold the two kinds of the front cover requires two kinds of the mold sets, and raises the manufacturing cost. Each mold in the mold sets is one piece including the subsidiary cores or cavities. If a small modification in an outer shape of a part to be molded is intended, each mold must be prepared again. There is an additional process of replacing the mold with a newly prepared one. A problem lies in delay or slow speed in supplying the front cover.